Method of removing gases and apparatus produced thereby.



W. D. COOUDGE. METHOD D F J?EMOVING GASES AND APPARATUS PRODUCED THEREBY.

- APPLICATION FILED OCT. 6, HHS.

1,323,836. Patented Dec. 2,1919.

,. UNITED STATES PATENT OFFICE.

WILLIAM D.

COOLIDGE, 0F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

PatentedDec. 2, 1919.

Application filed October 6, 1916. Serial No. 124,18.

To all whom it may concern:

Be it known that I, W LLIAM D. COOLIDGE, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in the Methods of Removing Gases and Apparatus Produced Thereby, of which the following is a specification.

The present invention relates to the removal of gases other than the rare gases, from an inclosed space, and is applicable both to the production and maintenance of very high vacua, and to the purification of the rare or noble gases, such as argon, neon, kr pton or.xenon.

The use of the metals calcium, magnesium, sodium and otassium has been suggested for the chemical removal of ases. ever, the high vapor pressure 0 these metals offers a serious drawback to their use for all purposes and particularly for certain types of electrical apparatus, having a very high vacuum.

I have discovered that the metals of the rare earth group, having a low vapor pressure, particlilarl thorium and zirconium,

are peculiarly we 1 suited for the removal of gases capable of chemical combination, such as oxy en, nitrogen, hydrogen, water vapor, the OXldS of carbon and the like. These metals form by combination with these gases chemically stable compounds of low vapor consists of tungsten or other suitable refractory material, and is connected to leads 4,-5, sealed into the envelop and connected to the members of a terminal 6, constructed similarly to an incandescent lamp base. The cathode is surrounded by a focusing ring 7 electrically connected to the cathode an supported by a stem 8, sealed into the lass stem 9. The anode stem 10 is carri by How an iron or molybdenum tube 11 fitted within a glass sleeve 12. The anode lead 13 is likewise sealed into the envelop and connected to an external terminal 14.

Preferably the bulb is first evacuated in the usual way to vacuum high enough to enable a pure electron discharge to be passed without positive ionization, as described by me, for examp e, in the Physical Review for December, 1913. Dry air or nitrogen is then admitted to the bulb and the thorium, zirconium or the like, preferably in a finely divided state, is introduced from a side tube, (as shown in connection with Fig. 2)' or, by cutting the connection to the pum he connection to the pump is reestablished if broken, and the bulb revacuated. Heat is then applied to the envelop wall adjacent to the metal powder 15, as by the use of an external gas flame, to start a reaction between the metal and residual gas within the tube including gases absorbed by the metal itself. The metal will be observed to glow as a reaction takes place and the result is a vacuum so high that no gas ionization effects can be observed when an electron current is transmitted.

Some of the metal appears to be deposited on the electrodes and other parts of the tube partly mechanically and partly by electrostatic attraction. The emissivity of the cathode when at incandescence is greatly increased by the presence of the thorium, or zirconium, de osited thereon so that a given current can Ee obtained at a much lower tern erature. The thorium on the cathode sur ace remains active in the very good vacuum maintained in the tube by the thorium or zirconium.

In Fig. 2 is shown a device filled with rare gas, such as argon, and used particularly as a rectifier, although it may have other uses, for example, as an oscillator. It comprises a bulb or envelop 1, an incandescent cathode 2, and an anode 3, both consistingpreferably of tungsten and sealed into thebulb as usual. ,Before evacuation a side tube 16 maybe aflixed containing the thorium or zirco ium, which later is introduced into the main ulb 1, as indicated at 15. The bulb is first baked out and evacuated in the usual way, dry argon, neon or the like is then admitted at a desired pressure, say, at several centimeters, and the thorium or zirconium is shaken over Into the main bulb.

The side tube 16 is then sealed off at the connection point 17 and is removed. External heating is aiplied to the material 111 the bulb until the desired reaction has taken place and the common gaseous impurities in the argon or the like have been removed by combination.

The excess of the thorium, or the like, remains in the tubeservin to combine with deleterious gases evolved from the electrodes or tube walls.

In the appended claims thorium is specifically mentioned but I mean thereby to claim also the utilization of equivalents, such, for example, as zirconimn, for the purposes of my invention.

'hat I claim as new and desire to secure by Letters Patent of the United States is: 1. The method of removing common gases from a device having a'cathode of refractory materialadapted to be operated at incandescence which consists in heating metallic thorium in said space to its reaction temperature. v

The method of producing a high vacu- 'um in a device having a cathode of refractory material adapted to be operated at ineandescence containing an attenuated atmosphere of common gases which consists in heating thorium therein to the reaction temperature.

3. The combination of a sealed envelop, cooperating electrodes, at least one of which is operable at incmnlescence and a quantity of thorium in a state of rendering it capable of combining with common gases.

4. The combination of an evacuated sealed envelop a cathode therein operable at incandescence, an anode and a quantity of metal of the rare earth group capable of combinin with common gases.

An X-ray device comprising a sealed, highly evacuated envelop, a ref 'actory cathode, an anodeor target, means for heating the cathode to incandescenee and a quantity of finely-divided thorium within said envelop.

(i. A vacuum device comprising a sealed exhausted envelop and a quantity of thorium within said envelop in a state adapted for combination with residual gas within said envelop.

In witness whereof, I have hereunto-set my hand this 5th da of October 19 16.

WILLIAM 1). COOLIDGE.

It isherehy certified that in Letters Pate t No. 1,323,836, g 'ented December 2, 1919, upon the application of William D. Cooiidge, of Schenectady, New York, for an improvement in "Methods of Removing Gase and Apparatus Produced Thereby," an error appears in the printed specification requiring correction as follows:

Page 2, line! 39- 40, claini '4, strike out the words "metal of the rare earth group and insert the words thorium in a stoic rendering it; and that the said Letters Patent should be read with this correction therein that the seine may conform to the record of the'cese in the Patent Oflioe.

Signed and sealed this 13th day of January, A. D., 1920.

' M. -H. COULSTON,

Acting C'mnuiiadomr of Patents. 

